1. Field of the Invention
The invention relates generally to a tubular connection for tubular members used in the oilfield. Specifically, the invention relates to a heavy wall connection for tubular members under conditions of high tension and high pressure which demand that heavy wall casing be used as production casing or tie-back casing in deep severe service oil or gas wells.
2. Description of the Prior Art
Downhole conditions in wells reaching depths over fifteen thousand feet include pressures approaching twenty-five thousand (25,000) psi and temperatures approaching five hundred (500) degrees fahrenheit. Downhole conditions are often characterized as severe when sweet gas C.sub.O 2 or sour gas H.sub.2 S is encountered. In order to withstand deep well and severe service conditions, the production casing is often required to be three times as thick as standard API walls for comparable outside diameter pipe sizes.
Inherent with the increased wall thickness required for deep severe service wells is increased string weight and rigidity of the tubular members. Prior art thick walled connections have had a tendency for thread jump-out and seal galling. These disadvangates of prior art connections for thick walled tubular members are attributable to positive flank thread profiles of the long tubular strings and the rigidity of the thick walled casings.
It is therefore an object of this invention to provide a thick walled tubular connection and pin and box members for that connection which overcome the disadvantages of the prior art connections.
It is a further object of this invention to provide a connection which allows for adjustment to tolerance variations in outside diameter and inside diameter of the pipe body without weakening the connection.
It is a further object of this invention to provide a tubular connection which reduces the susceptibility of the connection to stress corrosion cracking in a severe service environment.
It is still another object of the invention to provide a connection which inhibits excessive compression forces from radially collapsing the end of the pin member.
It is another object of the invention to provide a connection which creates axial compression of the internal surface of the pin thereby reducing the susceptibility of the connection to stress corrosion cracking in a severe service environment.
It is another object of the invention to provide sealing surfaces which increase the seal radial load distribution over that provided by prior art connections thereby reducing the tendency for galling by reducing peak seal load.
It is another object of the invention to provide a connection which combats the tendency for jump-out by locking the pin and box together thereby reducing collapse of the pin and expansion of the box.